Opinion for the Court filed by ROBB, Circuit Judge.
Special concurring opinion filed by MacKINNON, Circuit Judge.
Mr. Justice CLARK concurred in the opinion of the Court but died before it was entered.
ROBB, Circuit Judge:GAF Corporation (GAF) petitions for review of an order of the Occupational Safety and Health Review Commission (the Commission). The challenged order found GAF in violation of a regulation requiring em*22ployers to provide medical examinations to workers exposed to airborne concentrations of asbestos. GAF employees are exposed to asbestos dust during the manufacture of floor coverings and fiber building products. GAF contends that the Commission misinterpreted the regulation and that in any event the regulation is void. We conclude that neither of these contentions is correct and accordingly we affirm.
I. BACKGROUND
This dispute began in 1973 when the Secretary of Labor (the Secretary) issued citations charging GAF with violations of 29 C.F.R. § 1910.93a(j) (subsequently renumbered to § 1910.10010)).1 The cited regulation requires employers to provide certain pre-employment, annual, and separation medical examinations to all workers “in an occupation exposed to airborne concentrations of asbestos fibers . . . .”
GAF does not provide the specified examinations, but argues that the regulation does not require them, given the low levels of airborne asbestos at. GAF’s plants. At the time of the citation, which involved two of GAF’s plants, the level at both plants was below the maximum permissible level. (The maximum permissible level at that time was 5 fibers, of more than 5 micrometers in length, per cubic centimeter of air. See 29 C.F.R. § 1910.93a(b).) GAF contends that the regulations require medical examinations only if the concentration of airborne asbestos exceeds this maximum level or some other level higher than that found in GAF’s plants. The Secretary argues that the presence of any airborne asbestos at all triggers the requirement for medical examinations.
GAF challenged the citations throughout the levels of administrative review provided by the Occupational Safety and Health Act of 1970 (the Act), 29 U.S.C. § 659 (1970). In due course the Commission upheld the citations. Secretary of Labor v. GAF Corp., 75 OSAHRC Rep. 3/A2 (microfiche). GAF then petitioned this court seeking review of the Commission’s order as provided by the Act. See 29 U.S.C. § 660 (1970).
GAF contends that the Commission erred in interpreting the regulation to require medical examinations for employees exposed to the relatively low concentrations of airborne asbestos found in GAF’s plants. GAF also contends that the regulation is void because it was improperly promulgated, is inconsistent with the Act, and is arbitrary, irrational, and .unsupported by the evidence. We shall consider each of these contentions in turn.
A. Interpretation of the Regulation
We turn first to GAF’s contention that the Commission erred in upholding the Secretary’s interpretation of the disputed regulation. GAF is supported by neither the language nor the history of the regulation.
We note at the outset that the Secretary is charged by law with administering the Act and the regulations supporting it. 29 U.S.C. §§ 655 et seq. (1970). Hence, his interpretation of the regulation “becomes of controlling weight unless it is plainly erroneous or inconsistent with the regulation.” Udall v. Tallman, 380 U.S. 1, 16-17, 85 S.Ct. 792, 801, 13 L.Ed.2d 616 (1965). The Secretary’s interpretation remains controlling “even though the chosen exegesis may not appear quite as reasonable as some other construction.” [citation omitted] Budd Co. v. Occupational Safety and Health Review Commission, 513 F.2d 201, 205 (3rd Cir. 1975); accord, Clarkson Const’n Co. v. Occupational Safety and Health Review Commission, 531 F.2d 451, 457 (10th Cir. 1976). Furthermore, the standards must be construed, as they were construed by the Secretary, to protect the employees. See Brennan v. Occupational Safety and Health Review Commission, 491 F.2d 1340, 1344 (2d Cir. 1974).
*23The Secretary’s interpretation of the regulations not only satisfies the standards discussed above; it is far more reasonable than the interpretation urged by GAF.
GAF bases its argument upon the language of the regulation, which requires medical examinations for those “In an occupation exposed to airborne concentrations of asbestos fibers . . . .” 29 C.F.R. § 1910.93a(j). The Secretary interprets this language as requiring examinations for those in occupations exposed to any level of asbestos. GAF, in contrast, argues that the word “concentration” implies a quantitative amount. Because the disputed section does not specify any quantity of asbestos, GAF reasons that the section should be read to include the 5-fiber limit of 29 C.F.R. § 1910.93a(b), or at least some other quantitative limit greater than the level found in GAF’s plants.
GAF’s argument flies in the face of the language of the regulation. It would be a unique regulation indeed which managed to impose a quantitative limitation by not mentioning any quantity at all. Furthermore, a detailed examination of the regulation reveals that the omission of the quantitative limit was deliberate.
As originally proposed, the requirement of examinations was triggered by the presence of a specific quantity of asbestos:
Medical Examinations. The employer shall provide, or make available at his cost, appropriate medical examinations on a periodic basis to any employee who is exposed to asbestos dust in excess of the limits specified in paragraph (a) of this section [5 fibers per cubic centimeter].
37 Fed.Reg. 468 (1972).
The final standard, however, deletes the reference to a specific concentration. The preamble to the final standard notes that several changes have been made to the proposed regulation, and then states that medical examinations are now required for “every employee exposed to airborne concentrations of asbestos.” [emphasis supplied] 37 Fed.Reg. 11319 (1972). The preamble makes no mention of any specific quantity of asbestos. Nor does the final regulation itself. Instead, the final regulation requires examinations for those “in occupations exposed to airborne concentrations of asbestos fibers . . . .” The regulation states this requirement not once, but three times, in almost identical language: once each in the paragraphs requiring preplacement, annual, and termination examinations. See 29 C.F.R. §§ 1910.93a(j)(2)-(4). In contrast, 29 C.F.R. § 1910.93a(g)(1)(i) requires posting of caution signs “where airborne concentrations of asbestos fibers may be in excess of the exposure limits prescribed in paragraph (b) of this section.” [emphasis added]
We think these considerations leave room for only one conclusion: the disputed regulations require medical examinations for all those in occupations exposed to airborne asbestos in any measurable concentration.2
B. Validity of the Regulation
GAF contends that, even if the Secretary correctly interpreted the regulation, it is void on a number of grounds. We find this contention to be without merit.
Although we have carefully considered all GAF’s arguments concerning the validity of the regulation, only four merit discussion here. These are GAF’s contentions that the regulation is arbitrary and unsupported by evidence; that the regulation is inconsistent with the Act; that the Secretary’s interpretation is inconsistent with his approval of a California occupational safety plan; and that the federal regulation was improperly promulgated.
GAF argues first that the regulation is arbitrary and unsupported by evidence. GAF bases this argument partly upon the *24recommendation of the National Institute for Occupational Safety and Health (NIOSH). NIOSH was created by the Act for the purpose of developing health and safety standards and recommending them to the Secretary. 29 U.S.C. § 671 (1970). NIOSH recommended to the Secretary that medical examinations be required where airborne asbestos concentrations exceed 1 fiber per cubic centimeter of air. National Institute for Occupational Safety and Health, criteria for a recommended standard . . . Occupational Exposure to Asbestos at 1-3 (1972) [cited hereafter as “NIOSH criteria”]. The Secretary rejected this recommendation and instead required medical examinations for those exposed to any concentration of airborne asbestos.
GAF contends that this rejection by the Secretary was arbitrary and unsupported by the evidence, and especially arbitrary because NIOSH stated that its recommended standard included a “Safety factor”. NIOSH criteria at II — 2.
We have previously held that the Secretary is not bound by NIOSH recommendations. Industrial Union Department v. Hodgson, 162 U.S.App.D.C. 331, 340-41, 499 F.2d 467, 476-77 (1974). And in this case the Secretary’s departure from the NIOSH recommendation is reasonable. NIOSH noted that concentrations as low as 1.2 fibers per cubic centimeter have been known to cause serious diseases. Furthermore, NIOSH noted, the state of knowledge concerning asbestos-related diseases is such that no exposure standard other than zero would assure freedom from such diseases. NIOSH criteria at III — 23, III — 9. Hence the Secretary acted reasonably and on substantial evidence in requiring medical examinations for those exposed to any concentration of airborne asbestos rather than limiting examinations to those exposed to more than 1 fiber per cubic centimeter.
GAF argues next that even if the challenged regulation is supported by evidence, the regulation is invalid because it is inconsistent with the Act. GAF contends that the examinations are in effect being used as a form of medical research, because some useful knowledge will probably be gained from them. Under the Act, GAF continues, the Secretary of Health, Education, and Welfare (HEW) must pay for medical examinations used as research. Hence the challenged regulation, by requiring GAF to supply medical examinations at its own expense, contravenes the statute.
GAF misconstrues the Act and its effect upon the challenged regulation. The Act does not require the Secretary of HEW to pay for medical examinations used as research; it merely permits him to do so. The Act provides:
In the event such medical examinations are in the nature of research, as determined by the Secretary of Health, Education, and Welfare, such examinations may be furnished at the expense of the Secretary of Health, Education, and Welfare. [emphasis supplied]
29 U.S.C. § 655(b)(7) (1970). Thus, the Act clearly vests the Secretary of HEW with discretion to determine whether the examinations are in the nature of medical research and if so, whether to pay for them. His determination in this regard may be reversed only for an abuse of discretion.
We note initially that no decision of the Secretary of HEW in this matter is before the court. In any event, a review of the challenged regulation convinces us that the examinations in issue are not “in the nature of medical research” and are thus properly chargeable to GAF. GAF cannot seriously contend that the examinations are primarily designed to further medical research rather than to protect employees exposed to asbestos dust. As we have noted above, NIOSH found that non-zero exposure limits alone could not guarantee the prevention of asbestos-induced disease. NIOSH criteria at III — 9. Consequently, NIOSH recommended periodic medical examinations for the protection of the workers, noting:
The major objective of such surveillance will be to ensure proper medical management of individuals who show evidence of reaction to past dust exposures, either due to excessive exposures or unusual susceptibility. Medical management may *25range from recommendations as to job placement, improved work practices, cessation of smoking, to specific therapy for asbestos-related disease or its complications.
NIOSH criteria at 1-3. And in promulgating the final regulation, the Secretary of Labor noted the hazards connected with long-term exposure to asbestos dust and concluded, “the conflict in the medical evidence is resolved in favor of the health of employees.” 37 Fed.Reg. 11318 (1972). Finally, the Secretary specified in the regulation that records of the medical examinations in question would be kept by the employer, whereas the Act requires that records of examinations used as medical research be forwarded to the Secretary of HEW. 29 C.F.R. § 1910.93a(j)(6); 29 U.S.C. § 655(b)(7) (1970).
These factors considered together clearly indicate that the examinations at issue are to be provided primarily for the protection of GAF’s employees rather than for the purposes of medical research. Consequently, the challenged regulation does not contravene the section of the Act permitting the Secretary of HEW to pay for medical examinations conducted as medical research.
GAF argues that even if the challenged regulation is supported by evidence and consistent with the Act, the Secretary of Labor’s interpretation of the regulation is inconsistent with his approval of a California occupational health and safety plan.
The alleged inconsistency arises because the California plan, like the NIOSH recommendation for a federal standard, requires medical examinations only if the employees may be exposed to concentrations of asbestos greater than 1 fiber per cubic centimeter. General Industry Safety Orders 8 Cal. Admin. Code Ch. 4, Subch. 7 § 5208(j). The Secretary may approve of a state plan and permit the state to take over some enforcement functions of the federal government, but only if the state plan “provides for the development and enforcement of safety and health standards . . . which standards (and the enforcement of which standards) . . . will be at least as effective in providing safe and healthful employment ... as the standards promulgated under section 655 of this title . . .” [emphasis supplied] 29 U.S.C. § 667(c) (1970).
The Secretary has approved the California plan. 38 Fed.Reg. 10717-20 (1973); 41 Fed.Reg. 1904-06 (1976). This approval, GAF argues, indicates that the California plan is “at least as effective” as the federal scheme. Consequently, GAF contends, the Secretary’s approval of the California plan is a tacit admission that the federal regulation does not require medical examinations when asbestos concentrations are less than 1 fiber per cubic centimeter.
We cannot agree with GAF’s reasoning. In approving the California plan, the Secretary clearly evaluated the plan as a whole, discussing not only limits for various toxins, but enforcement, notice, record-keeping, and sanction requirements as well. 38 Fed.Reg. 10717-20 (1973); 41 Fed.Reg. 1904-06 (1976). The Secretary noted that California would provide more enforcement personnel than the federal program. 38 Fed.Reg. 10718 (1973). Hence, it was reasonable for the Secretary to conclude that the California standards as enforced would be “at least as effective” as the federal standards despite differences in the triggering concentrations of asbestos.
GAF argues finally that, even if the Secretary correctly interpreted the federal regulation, and even if the regulation is consistent with the Act, supported by the evidence and consistent with the California plan, the federal regulation is void because it was improperly promulgated. GAF’s argument is as follows: the Act requires that each proposed regulation be published in the Federal Register to permit public comment. 29 U.S.C. § 655(b) (1970). In this case the Secretary published a proposed regulation but then made changes in it before publishing it in final form. GAF argues that the amended rule should first have been published as a new proposed rule, with opportunity for public comment before being promulgated as a final regulation.
*26The short answer to this contention is that GAF never raised this objection before the Commission and is therefore precluded from raising it here. The judicial review provision of the Act provides that “no objection that has not been urged before the Commission shall be considered by the court . . . 29 U.S.C. § 660(a) (1970). Furthermore, as this court has previously noted:
The requirement of submission of a proposed rule for comment does not automatically generate a new opportunity for comment merely because the rule promulgated by the agency differs from the rule it proposed, partly at least in response to submissions.51
* * * * * *
International Harvester Co. v. Ruckelshaus, 155 U.S.App.D.C. 411, 428, 478 F.2d 615, 632, n. 51 and accompanying text (1973); accord, South Terminal Corp. v. E.P.A., 504 F.2d 646, 659 (1st Cir. 1974). We think the same principle governs GAF’s contention in this case, and accordingly we reject GAF’s argument.
In conclusion, we hold that the Secretary’s interpretation of the disputed regulation is reasonable, and that the regulation is supported by the evidence, consistent with the California plan, and was properly promulgated. GAF’s petition to review and reverse the decision of the Occupational Safety and Health Review Commission is denied.
So Ordered.
. 29 C.F.R. § 1910.93a was recodified as 29 C.F.R. § 1910.1001 on May 28, 1975. 40 Fed. Reg. 23072 (1975). The regulation will be cited throughout this opinion as § 1910.93a, to reflect the codification in effect at the time of the alleged violations.
. We are aware that the Occupational Safety and Health Review Commission of the state of Connecticut reached a contrary conclusion in interpreting a state regulation virtually identical to the federal regulation before this court. Commissioner of Labor v. Tuttle & Bailey Division of Allied Thermal Corp., Docket No. 76-315, December 3, 1976. Nevertheless we feel that the deference due the Secretary’s interpretation, along with the plain language and history of the federal regulation, compel the conclusion we reach here.
A contrary rule would lead to the absurdity that in rulemaking under the APA the agency can learn from the comments on its proposals only at the peril of starting a new procedural round of commentary, [footnote in original]